1. Field of the Invention
The present invention relates to an assembly packaging method for a sensor element and, more particularly, to the improvement of a method of mounting electrodes to a sensor chip and coating the sensor chip for insulation to complete a sensor element.
2. Description of the Prior Art
As a sensor for detecting the intensity of a magnetic field, hole elements and magnetoresistive elements have been developed and used for a sensing detector in the field of robotics science or the like.
FIGS. 5A to 5C schematically show the conventional process for producing a magnetoresistive sensor.
A compound semiconductor thin layer is first formed on a base plate and subjected to a precision working such as photoetching to produce a sensor chip 1 provided with a predetermined sensing function as shown in FIG. 5A. Thereafter, lead frames 2 for connecting the sensor chip 1 to external elements are mounted on the sensor chip 1 (FIG. 5B) and the sensor chip 1 is coated with a protective insulating layer 3 (FIG. 5C) so as to complete a magnetoresistive sensor element.
By this process, a sensor 4 provided with the lead frames 2 mounted and the protective insulation coating 3 is secured to a predetermined data processing circuit board or print circuit device 5 or base in accordance with a given purpose of use, as shown in FIG. 6.
A conventional sensor having such a structure, however, is defective in that the mechanical strength at the connecting portion of a lead frame is so weak for using hard metal lead frame wires that the lead frame is apt to be easily broken. In addition, in the sensor chip with the lead frames mounted thereon, since the hard metal lead frames project sideways from the edge portions of the sensor chip, as shown in FIG. 5(C), it is impossible to obtain the standardized arrangement of pins to be connected to connectors, so that the handling of the assembly packaged chip cannot be automized and, hence, inconveniently requires manual operation.
Furthermore, in the conventional method, a protective insulation layer must be formed on the sensor chip after the lead frames are mounted thereon one by one. This assembly process must be repeated for each chip, which is the main factor of deterring the mass production and the reduction in cost of sensor chips.
In a conventional magnetoresistive element, for example, an insulation layer for insulating the sensor chip is formed on the chip surface by coating from the outside. Actually, however, the uniform coating cannot be realized for the insulation and, as a result, when the magnetoresistive element is used as a precise position detection sensor, the uneven surface of the insulation layer makes the magnetoresistive characteristic of the sensor unstable.